The invention is related to a robot of an orthogonal coordinate type performing rectilineal movement along three axial coordinates, and particularly, to provide a rectilineal movement speed enhancing apparatus for an orthogonal coordinate robot.
A conventional orthogonal coordinate robot constitutes a mechanism performing rectilineal movement in three axial directions, in which it has three degrees of freedom respectively associated with up and down movements, left and right movements and fore and aft movements to take a product out from a system. The orthogonal coordinate robot usually has an independent freedom degree for one axis, which comprises a frame, one power driving source, a rack connected to the power driving source and a threaded portion engaged with the rack so that it is constructed as a simple rectilineal movement mechanism. The orthogonal coordinate robot has a disadvantage in that the moving distance of an arm or its stroke is usually limited.
A typical prior art proposal to resolve that disadvantage is made in Japanese Patent Laid-Open Publication No. 89-246084. This patent discloses a rectangular coordinate type robot for increasing the stroke length of an arm, in which a main ball screw is rotated by the drive of a drive motor, a main arm is moved relatively to a first arm by this rotation, the rotation of the main ball screw is transmitted by transmission mechanisms to a rotary member, and a follower arm integrated with a follower ball screw to be engaged with this rotary member is moved to the main arm in the same direction as the motion of the main arm.
But, that robot is very complex in its configuration because of requiring numerous parts such as the follower arm associated with the main arm, the follower ball screw with respect to the main ball screw, a power transmitting device for transmitting the power of a main driving source to the follower arm, etc.
Also, another method can be adapted to an orthogonal coordinate robot in order to obtain the benefit of extending the movement stroke, in which the robot comprises two unit rectilineal movement modules in the form of block structures which are constructed in a series arrangement. To this end, the robot employs two driving sources, frames moved by the two driving sources, respectively, a system for sensing the excessive movement of the frame etc. So, the robot firstly forces one unit rectilineal movement module to be operated in order to obtain a relatively longer stroke, and then after the completion of the movement of the frame, another unit rectilineal movement module must be moved. However, it has a disadvantage in that the movement speed is slow. To overcome this defect, the speed of the driving source can be selected with respect to the stroke to be increased. But in respect of its total configuration, it requires separate parts which causes the robot to be more complex as well as difficult to manufacture.